New Atom-Smashing Magnet Passes First Tests

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A powerful new magnet to replace existing ones in the world's
largest atom smasher, the Large Hadron Collider, just passed its
first test with flying colors.

The magnet, which allows the massive particle collider to study
two to three times more proton collisions, could help unveil the
mysterious properties of the newly discovered
Higgs boson, an elementary particle that is thought to
explain how all other particles get their mass.

The new magnet produces a much larger magnetic field to focus the
proton beams into an even more miniscule area, thereby ensuring
that more protons crash into each other.

Focused beams

Right now, the Large Hadron Collider uses a magnet to focus the
proton beams before they smash into each other. The farther the
protons deviate off course, the stronger the magnet pulls them
toward the center of the beam that's just a few thousandths of an
inch wide. Though hundreds of billions of protons make up each
beam, there are still relatively big empty spaces between them,
meaning the odds of a collision are relatively small.

The current magnet is made of a superconductor called niobium
titanium, which, when cooled to near absolute zero, allows large
amounts of current to flow without overheating.

Niobium titanium was fine for simply discovering the Higgs boson,
but revealing the properties of the Higgs boson requires more
collisions than the LHC currently allows.

"The LHC is already designed at the limit of the technology,"
said GianLuca Sabbi, an accelerator physicist at Lawrence
Berkeley Laboratory who helped design the new magnet. "So how do
you make it better?"

One of the top candidates was niobium tin, which can produce a
higher magnetic
field and more current at higher temperatures.

But superconducting coils made of niobium tin are more brittle
and therefore prone to moving in response to the huge forces
generated as the magnet turns on. That, in turn, could release
energy in the form of heat and cause the magnet to lose its
superconductivity.

Higher-power magnets also cause more radiation of subatomic
particles during collisions, which can damage the magnet more
quickly.

To solve these problems, the team built a thick aluminum shell to
support the niobium tin superconductor and prevent its
displacement.

The new magnet and its housing can produce magnetic fields 50
percent stronger than the LHC's current magnet. That extra
strength translates to two or three times the number of
collisions, Sabbi said.

But the LHC has a bigger goal: Over 10 years, researchers plan to
revamp the entire system to achieve 10 times as many collisions.

"The magnets are just one element of many changes that are going
to be made in the machines," Sabbi told LiveScience.